Photoinduced decarbonylation from carbonyliron tetraphenylporphyrin in ethanol. Effects of axial imidazole studied by laser flash photolysis
Journal Article
·
· Journal of Physical Chemistry
- Inst. of Physical and Chemical Research, Saitama (Japan)
- International Christian Univ., Tokyo (Japan); and others
Photochemical reactions of carbonyliron(II) tetraphenylporphyrins, (CO)(L)Fe{sup II}TPP (L = ethanol and imidazole) and bisimidazoleiron(II) tetraphenylporphyrin, (Im){sub 2}Fe{sup II}TPP, in ethanol were systematically investigated by laser flash photolysis. The yields for photodissociation of CO from (CO)(C{sub 2}H{sub 5}OH)Fe{sup II}TPP and (CO)(Im)Fe{sup II}TPP were determined to be 0.53 and 0.9 at room temperature, respectively. On the basis of the quantum yield measurements in the temperature range 180-300 K, the activation energies for decarbonylation obtained for (CO)(C{sub 2}H{sub 5}OH)Fe{sup II}TPP and (CO)(Im)Fe{sup II}TPP were 0 and 4.9 kcal mol{sup {minus}1}, respectively. No dissociation of the ligand L from (CO)(L)Fe{sup II}TPP was detected. The photochemical dissociation of the axial imidazole from (Im){sub 2}Fe{sup II}TPP was also studied. The yield for photodissociation of imidazole obtained was 0.18 at room temperature, and the activation energy was evaluated to be 2.6 kcal mol{sup {minus}1}. It was found that (Im)(C{sub 2}H{sub 5}OH)Fe{sup II}TPP produced by photolysis of both (CO)(Im)Fe{sup II}TPP undergoes spontaneous base elimination to give (C{sub 2}-H{sub 5}OH){sub 2}Fe{sup II}TPP and imidazole, Im. The reactive excited states responsible for photodissociation of the axial ligands as well as the spontaneous base elimination reaction are discussed in detail. 33 refs., 11 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 458805
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 22 Vol. 96; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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